Window envelope and method of making the same



March 9, 1937. R. L. GRAY 2,072,875

WINDOW ENVELOPE AND METHOD OF MAKING THE SAME Filed Sept. 25, 1931 3 Sheets-Sheet l 24 3233/4 3; 2,3 3 -7 /7 f %Q%VAV%%%%%W//J/ faif/PrZ 5645.

dummy 7 VACTl/UM 670/7405 March 9,1937. R, L, GRAY 2,072,875

WINDOW ENVELOPE AND METHOD OF MAKING THE SAME Filed Sept. 25, 1951 s Sheets-Sheet 2 fuzz/P71. 6:647,

and

March 9, 1937. R. L. GRAY 7 WINDOW ENVELOPE AND METHOD OF MAKING THE SAME Filed Sept. 25, 1931 3 Shqets-Sheet 3 swank faizir Z. G/P/ry,

Patented Mar. 9, 1937 PATENT OFFICE WINDOW ENVELOPE AND METHOD OF MAKING THE SAME Robert L. Gray, Brooklyn, N. Y. Application September 25, 1931, Serial No. 565,038

25 Claims.

This invention relates to a method of forming window envelopes and the resulting product.

It is an object of my invention to provide a window envelope construction which may be generally. designated as a two part envelope in that the window portion covering the opening, defining the section of the envelope through which the addressed contents may be viewed, is not made integrally with, or from the fabric of the envelope itself. The two part envelope of the character referred to is preferred by me in that the envelope structure itself, may be made of any desired paper or similar fabric, without limitation, and is superior to the one piece envelopes wherein translucency is obtained at the window portion by oiling the paper. This preference is due to the limitation of the paper that can be used and the limited transparency of the result-'- ing product where the window portion and envelope are of integral construction. A further preference to a two part envelope construction resides not only in the ability to use any desired fabric for the envelope per se but the nature of the transparency which may be attached is far superior to that attainable from making the same from the body portion of the envelope itself.

Wh'ere I have attempted to adhesively conn'ect a transparent sheet to the envelope adjacent the cut out portion, constituting the window,

with speeds of operation commercially and economically practicable, the gluing operation incident to adhesively connecting the transparent strip over the opening of the envelope and the method of its application, has resulted in an undesirable article in that a continuous seal about the opening is not obtained; the process does not lend itself to speed of operation; the excess adhesive, when the same is applied in a solution, 4" usually overruns the edges of the patch and forms an objectionable envelope, when completed. Insufficient use of a solution of an adhesive to overcome this defect for attaching the transparent patch over the cut out portion of the envelope results in loose ends in the interior of the envelope, which interfere with the insertions of the contents for mailing purposes.

It is therefore contemplated by my invention to provide a window envelope construction in which the transparent portion of the window or opening is of dissimilar material from the body of' the envelope, whereby any desired type of transparency may be utilized and to attach the same as a patch over the cut out portion of the envelope, theadhesive contact in the position aforementioned being characterized by a tenacious and firm bond equivalent to welding, and. in which loose edges are entirely avoided and extraneous adhesive eliminated.

It is a further object of my invention to pro- 5 vide a method for adhesively attaching a patch to a window envelope which will lend itself to high speed production, characterized by providing a pre-treated transparency, including an adhesive which may be activated to adhesive- 10 ness by heat and applying a transparent sheet thus formed in position over the cut out portion of an envelope merely by the application of heat with or without pressure. The process is further characterized by the'ability to imme- 15 diately follow such operation by operations to completely finish the envelope, without any substantial interval of delay whatsoever, in that the removal of the pressure incident to applying the patch completes the operation and re- 20 quires no' interval for setting the adhesive in position.

Other objects of my invention reside in the provision of a window envelope in which a highly transparent material, such as regenerated ceilulose, known as Cellophane" may be used as the transparency thereof and the transparent sheet tenaciously adhered as a patch, permitting the use of any desired body fabric for the envelope, characterized by initially coating the 30 transparent material with a coating which in the final form results in a normally dry adhesive, which is responsive to heat, to be act ivated to adhesiveness but which does not in any way interfere with thetransparency of the sheet, the method being characterized by positioning a transparent sheet, such as regenerated cellulose, waterproofed or otherwise, carrying a normally dry adhesive, applying the sheet thus formed in position and then activating to adhesiveness those portions of the patch which contact with the fabric of the envelope by the application of heat, preferably simultaneously with pressure, to thereby efiiciently and eflectively unite or weld the patch in position. 45

. Other objects of my invention reside in the provision of a method for effectively and tenaciously uniting a transparent patch to the window portion of an envelope by interposing between a transparent sheet and the body of the envelope, a normally dry adhesive material, activating the material to adhesiveness by heat and then applying pressure to unite the patch to the body of the envelope, whereby the contacting surface portion of the patchis effectively held in position, with- 55 To attain these objects and such further objects as may appear herein or be hereinafter pointed out, I will now refer to the accompanying drawings, forming a part hereof, in which- Figure 1 is a diagrammatic illustration of apparatuswhich maybe employed for preliminarily coating the transparent sheet;

Figure 2 is a diagrammatic illustration of the severing and envelope uniting apparatus;

Figure 3 is a fragmentary plan view of an envelope blank and transparent patch in accordance with my invention, the patch being partially removed;

Figure 4 is a section taken on the line 4-4 of Figure 3;

Figures 5, 6, and '7 are plan views of the envelope blank invarious conditions of manufacture, for illustrating another embodiment of my invention;

Figures 8, 9, 10 and '11 are plan views of an envelope blank in various conditions of manufacture, with still another embodiment of my invention.

In the preferred embodiment of my invention, it is contemplated by me to first provide a web of transparent sheeting, such as waterproofed, regenerated cellulose, known on the market as Cellophane", or other similar transparent sheets as glassine paper as the material from which the patch for the window envelope is to be made.

The sheet so provided is preferably coated on one side thereof, with an equally transparent coating of material which may be activated into adhesiveness, but which normally is dry and nontacky to the touch.

As one example of forming a product as indicated above, it is preferred by me to coat the transparent sheet of the character indicated, with a thin, transparent coating of animal glue suitably gelatinized or softened by such agents as a small quantity of glycerine. This coating comprising the adhesive material of animal glue and softening agent, is preferably one which may be activated to adhesiveness by heat, but at normal room temperature, is dry and free from tackiness.

As another-example of a form of transparency or transparent sheet which I may utilize, ,1 prowide glassine paper of suitable transparency,

coated on one side with a thin transparent film of glue of the character above indicated. This glue coating preferably is one which responds to a temperature of about 135-200 R, to be rendered sufilciently plastic to become adhesive, but at normaltemperatures is dryv and non-tacky to the which may be desirable for my purposes. ations of the glycerine and water content may .be

made in accordance with the degree of sensitivity of adhesiveness to heat which is desired. Thus,

by increasing'the glycerlne content, a more plastic and more readily heat responsive adhesive coating is obtained and, conversely, with a reduction-of the glycerine content, a coating less responslve to heat may be obtained.

It is contemplated by me' to include as an ad hesive surface such modifications of these ingredients which will be responsive to heat withweb i6 passing between the rolls l3-l3.

web carrying the coating I5 is then submitted to out marring or injuring the paper or transparency to which it is attached, to have the exposed surface thereof unresponsive to room temperatures or body heat to tend to render the same tacky, and at the same time be quickly responsive hesively activated when heated, such as rosin, rosin substitute, such as phenolic-condensation resins; varnishes, such as mixtures of a drying oil and a resin. Also, the transparency which I may use may be a thin film of flexible gelatine, preferably waterproofed on both sides with a drying oil, andcoated on one side with the adhesive film, which is responsive to heat to become plastic for adhesively uniting the transparency to the envelope blank.

As a furtherexample, I may enumerate transparent materials made from hydrated cellulose coated with an adhesive film whichis responsive to heat to become activated to adhesiveness, such as by coating thereon a film of glue, as in the prior embodiments; or one including a coating of .an oil or resin varnish, a resin substitute or a thin sheet of pyroxylin or plasticized cellulose which becomes readily responsive to heat to become adhesive.

A web or material thus provided, may then be utilized as a patch material to cover the opening or cut out portion of a blank from which an envelope is made. The transparent composite is positioned over the cut out portion of the blank,

and a section sufficient to cover this cut out portion is then severed. That section of the patch overlapping the walls and body portionof the envelope blank is then heated to a temperature sufiicient to activate the adhesive coat which is interposed between the transparent material and the body of the envelope. Pressure is then applied to tenaciously and' adhesively contact the patch to the envelope body and effectively unite the same to the fabric of the envelope and weld the patch in position upon the envelo e. The composite thus formed may be then immediately submitted to the usual envelope forming opera tions, to completely form the envelope.

Where I desire to manufacture the article by a continuous operation suitable for quantity production, in one embodiment thereof,the method may be practiced as hereinbelow indicated, referencebeing made to the accompanying diagrammatic drawings, for purposes, of simplifying the consideration of this process.

A roll A constituting a ribbon or tape of transparent sheeting is provided. This may be regenerated cellulose, waterproofed or otherwise treated, nitrocellulose film,'modified paper or other transparent or semi-transparent sheeting above enumerated. The web'so provided is fed to a coating device and in the illustrationythe coating device constitutes a. roller applicator [0 in which animal glue with a softening agent is maintained fluid by being heated within the tank ii. The applicator rolls l2 serve to transfer a thin, even and uniformicoating of the gum to the rolls i3, which in turn transfer the same to the The a setting treatment. This I accomplish by passto temperatures of the character above indicated,v

ing the web through a chamber I 6 which serves to set and harden the coating I5, and for this purpose, the chamber I6 is maintained with dry air and at a low temperature. The web l4 emerging from the setting chamber l6 does not have its transparency substantially modified by the coating of gum carried by it. This gum coating is now in a condition resulting from this treatment, wherein it is normally dry and free from tackiness. In this condition, if desired, the web may be again formed into rolls for use at some time subsequently, in accordance with the process which will hereinafter be described.

Preferably, however, the web may be directly fed to an assembling table ll (see Fig. 2). Upon this table there may be provision for positioning securely an envelope blank l8, of the character normally used for making window envelopes.

v velope.

to a chamber 22, which is connected with a timed suction device 23, as will appear hereinafter. The table I'ii is preferably provided, at its upper face, with a depressed portion 243. This depressed portion corresponds substantially in outline to the window opening I9 in the envelope blank. It is preferred that the envelope blank l8 be positioned so that the cutout window opening I9 is in alignment with the depressed portion 26 on the table. The envelope blank may be fed to this position by suitable feeding means, such as gripper fingers timed in proper relationship to the remainder of the mechanism.

When the envelope blank is thus positioned, the strip' of transparency, preferably carrying the heat'responsive coating 15, is fed by intermittent feeding rolls adjacent complemental cutting members 26. The cutting members 28 are timed also has sufficient overlap over the window open ing, as will be readily understood.

By this operation a length Me is severed and this section Ma is picked up by the plunger 21?.

. The plunger 21, more specifically illustrated in Figure 2, constitutes a housing hollow at 28 and connected through the pipe. 29 with a suction line 30. The hollow portion is' connected to the face 3| of the plunger by a series of orifices 32. The

plunger also includes a depressed or heat insulated portion 33, the outline of which corresponds to the window opening IS in the envelope blank. The outline of the plunger 21 at the face 3| corresponds substantially exactly to the di-' mension of the patch Ma, whichhas been severed.

It will be understood that suction from within the temperature of from about 135 to 200 F., the

range thus provided depending upon atmospheric I I conditions and thecharacter of adhesive coating carried by the patch and allow also for radiation tending to cool the plunger. I

In this position, the plunger carrying the patch Ila is then reciprocated downwardly upon the table II. At reaching this point, suction is maintained within the chamber 22 to not only fixedly hold the blank l8 in position but also to hold the patch 14a flat on the blank l8. Upon continuing the movement of the plunger 21, the patch Ma. is forced into contact with the blank l8. The interval of time for moving the patch into position and that for pressing it'against the blank I8 is suflicient to have the heated plunger render the adhesive coating-l5 sufficiently adhesively energetic and plastic to assure firm union and welding of the patch and the envelopeblank. At this moment, suction in the line 30 is released and then the reciprocation of the plunger is reversed to move away from the table II. The release of the patch from the face 3! of the plunger 21 is facilitated by a pair of spring fingers 36, retained within the recessed portion 33. The action of the spring fingers 36 may be additionally facilitated by blowing air through the line 30. In the drawings timed suction for the operation described is accomplished at the proper moment by valves V22 and V28 each connected to vacuum storage tank 'I operated by the pump P. i

As separation of the patch has thus been effected, suction within the chamber 22 is released and suitable means may be used to remove the envelope blank l8, with the affixed patch I la to the other portions of the machine for completing the forming operation of the envelope.

It will be further understood that where the temperatures of the plunger 2! are sufficient to have a tendency to modify the paper or the size carried thereby to' adhesiveness when in contact with the face 3| of the plunger, any tendency of the patch Ifla' to adhere to the face may be overcome-by dusting talc or similar material to the face 3!, at frequent intervals. 4

Though, by the method above described, it is contemplated by me to utilize as the transparent sheet, for union thereof with the envelope blank,

one which includes a preliminary treatment with a coating I 5 which is normally dry but which may be activated to adhesiveness by heat, it will -be understood that the adhesive coating may be a separate dry adhesive sheeting fed into position simultaneously with the feeding of-trans- 'parency, but interposed between the transparency and the envelope blank. Also though I have described as my preferred form a sheet is of transparent material and embodied therewith a dry coating of material which is activated by heat, the coating may be wet by application 'of a solution of adhesive but losing its fluidity and becomes plastic or semi-solid upon contact of the patch carrying this coating with plunger 21.

Furthermore, though I have described as the preferred form of my invention, the application of a'patch Ida carrying a coating of adhesive material which maybe activated to adhesiveness by heat, in another embodiment of my invention the transparency need not be. treated in this manner, but may be free from any coating whatsoever.

In such additional embodiment of my invention, I provide an envelope blank 31, such as shown in Figure 5, comprising the usual seal flap 38 and side flaps 39 and back flap 40. This is provided with a window opening l9. This blank, at the time of forming the envelope, is provided with glue coating by suitable applicators so that the seal flap 38 has applied a layer of glue 42; the back flap has applied thereto a layer of glue 43 and the overlap portion immediately surrounding the window opening I9 has also applied thereto a layer of glue or similar adhesive 44. It will be understood that the layers 32 and 43 may be of dissimilar character since the seal flap is intended to remain normally dry whereas the back flap adhesive coating 43 is utilized to permanently adhesively connect the side flaps 39. The layer of adhesive Q4, applied to the overlap portion surrounding the opening I9 is preferably treated to become normally dry and is of the character when dry to be readily responsive to heat, to become adhesive. The blank thus formed may then be submitted to the patch applying process described, using, however, a web of transparency. which is untreated and preferably, however, though not necessarily so, without the dry coating of adhesive material. The process,however, in all other respects is identical, and in Figure 7 the final product just prior to the forming of the envelope is illustrated, wherein the transparency I4 is shown ailfixed in position and overlying the window opening l9. v

In a still further embodiment of my invention illustrated in Figures 8-11, an envelope blank $5 is provided. This includes the usual form of seal flap 45, back fiap 41 and side flaps 48. The

blank so formed is then passed through a. series of outlining applicators whereby the seal flap 46 has applied at its edges a layer of glue 49; the

flap 41 has applied thereto a layer of glue 50 and the body portion 'of the blank has applied thereto a layer of adhesive material 5|. This layer preferably takes the outline, in sizeand shape,

of the transparent patch I4 to be applied. The nature of the adhesive coatings 49 and 50 is similar to those previously described, suitable for use in connection with the back flap and seal flaps; The layer of adhesive 5|, however, is such as to become, in the further processing of the envelope blank, normally dry and non-tacky but 'is of the character which responds readily "to temperatures of the character previously indicated, to become adhesive. The blank thus formed-is then perforated by providing the window opening IS'within the confines ofthe layer 5| of adhesive material. The envelope blank thus providedis then submitted to the patch applying processof the character previously described, wherein a transparent patch I4 is aligned with the adhesive coating 5| and then at fixed in position by heating.

It will be understood that in the embodiments illustrated in Figures 5-11, the adhesive coatings 44 and 5|. need not be applied in a continuous coating but may be in the form of dusted or 'pulverulent material, the material used, however,

being one which responds" to heat to become ad- I hesive but 'isnormally non-flowing.

By the apparatus diagrammatically illustrated,

and the-process described, the transparent patch I4 is properly affixed in position to the envelope over the opening l9. The employed method of application of this patch results in a uniting .action equivalent to welding of the patch to the face of the paper or fabric constituting the material from whichthe envelope itself is made.

Since the heating operation resulting from conunite the patch in position.

tacting the heating unit to the back surface of the patch has been sufflcient to merely render the adhesive coating l5 in a condition where it is responsive to pressure, no excess material will reversal of the operation, whereby the body 01.

the envelope is heated by the table Il,*comes within the scope of the invention described.

By the method described for applying the patch to the face of the envelope, the union of the patch and the fabric from which the envelope is made, is in effect a welding operation in that the plasticity of the adhesive and to a certain extent the layers united are overcome by heat and pressure employed. The operation being carried out without any extraneous moisture results in an envelope blank which is free from any warped condition of either the patch or the composite of envelope and patch, thereby facilitating the handling of the envelope blank and assuring maximum strength and transparency of the unsupported portions of the patch over the opening ,of the envelope.

Though I have described one form of apparatus for carrying out'the methods employed, this will be understood to be exemplary only and that the details of such apparatus and others may form a part of other independent inventions contemplated by me for the use in practicing the present invention herein described.

Having thus described my invention and illusto secure by Letters Patent, is-.

1. A method of making window envelopesfrom an envelope blank and patch of dissimilar material whichincludes, applying a patch comprising a transparency over the window portion of the envelope, said patch including an interposedv adhesive material, and heating the' composite to 2. A method of making window. envelopes: which includes applying a patch comprising a flexible transparency over the window portion of the envelope, interposing a. normally dry adhesive material and uniting said patch to said envelope by heating the adhesive material.

trated its use, what I claim as new and desire 3. A method. of making window ehvelopesfrom an envelope blank and patch of dissimilar material, which includesapplying a patch comprise ing a flexble transparencyover the window portion of the envelope, interposing a normally dry adhesive material and uniting said patch to said envelope by heating the adhesive material, the

heating including pressing theheated portions into contacting engagement.

4. The method of making window envelopes from an envelope blank and patch of dissimilar material, which includes preliminarily providing a flexible transparency 'with a transparent normally dry coating, comprising an adhesive that is heat plastic, positioning the transparency in po-. sition over the window portion of the envelope, and hot pressing under pressure to unite the patch and envelope.

5. The method-of making window envelopes from'an envelope blank and patch of dissimilar material which includes applying a patch, comprising a transparency over the window portion thereof, interposing a fusible adhesive, and uniting the patch by fusing the adhesive.

6. The method of making window envelopes from an envelope blank and patch of dissimilar material which includes applying a patch, comprising a transparency over the window portion thereof, interposing a fusible adhesive, fusing the adhesive, and applying pressure when the adhesive is in the fused condition to unite the patch and blank without edges interfering with insertions into the finished envelope.

7. The method of forming window envelopes from an envelope blank and patch of dissimilar material which includes aiiixing a patch, comprising a transparency over the cut out portion of a blank, -with-portions of the patch overlapping, interposing a fusible adhesive at such overlapped portions, and uniting said transparency to said envelope under heat and pressure. a

8. ,The method of. making window envelopes from an envelope blank and patch of dissimilar material which includes overlaying over the cut out portion of said envelope blank a flexible sheet of transparent material, having a normally dry coating of a fusible adhesive material and fusing the coating on the transparent material in the position aforesaid to unite the transparent sheet to the envelope.

9. The method of making window envelopes from an envelope blank and patch of dissimilar material which includes overlaying over the cut out portion of said envelope blank a flexible sheet of transparent material having .a normally dry coating of a fusible adhesive material and fusing by heating the coating on the transparent material in the position aforesaid to unite the transparent sheet .to the envelope.

10. The method of making window envelopes from an envelope blank and patch of dissimilar material which includes overlaying over the cut out portion of said envelope blank 2. flexible sheet of transparent material having a normally dry coating of a fusible adhesive material, uniting the transparent sheet to the envelope while maintaining the adhesive material in a fused condition.

11. The method of making window envelopes which includes overlaying over the cutout portion of said envelope blank a flexible sheet of transparent material having a normally dry coating of a fusible adhesive material, uniting the transparent material in the position aforesaid while heating the adhesive material and applying pressure during the heating process.

12. The method of forming window envelopes from envelope blanks of substantially opaque material which includes overlaying over the cut out portion of said envelope blank a flexible sheet of transparentcellulosic material, interposing a dry fusible adhesive material between said transparent material and envelope blank, and uniting said transparent material to said envelope under heat and pressure while said adhesive is in a.

fused condition.

13. The method of forming window envelopes [from envelope blanks .of substantially opaque material which includes overlying over the cut out portion of said envelope blank a flexible sheet of transparent, cellulosic material having a normally dry coating of a fusible adhesive material, disposing theflexibl'e material to overlap a portion of said blank and heating the composite on said overlapped portions to fuse the adhesive and applying pressure to unite the transparent sheet to the envelope.

14. The method of making window envelopes from'an envelope blank and patch of dissimilar material which includes overlaying over the cut out portion of said envelope blanka flexible sheet of transparent cellulosic material, interposing a fused adhesive material between said transparent material and envelope blank and uniting by application of pressure. I

15. A window envelope comprising a separately attached patch of transparent material overlying a cut out portion of .the envelope blank, said patch being united to the blankby fused adhesive in position adjacent the cut out portion of the envelope blank.

16. A window envelope including a separately formed transparency and envelope body blank, the transparency being united to said blank by a film of fused adhesive between the transparency and the body blank.

17. A window envelope comprising a separately formed envelope blank and transparent sheet overlying the cut out portion of said envelope, the transparent sheet being united at a peripheral edge by a fused adhesive to avoid edges interfering with the filling oi the envelope.

18. In the method of forming window envelopes of the two-piece type from a separately formed envelope blank having a cutout and a substantially transparent patch of a size to overlap the cut out, the steps which comprise overlaying the patch over the envelope blank adiacent'the cutout, the patch having an interposed adhesive material substantially completely covering the entire patch, activating the adhesive material to tackiness and during the active condition of the adhesive, uniting the patch to the blank by pressure applied to substantially the complete outline of the patch to seal the patch and blank at the portions which overlap without any loose edges at the cutout, and without any loose edges at the periphery of the patch which may interfere with the insertion of the material into the completely formed envelope.

19. In the method of making window envelopes formed of a paper envelope blank and a. substantially transparent patch, the steps which include a patch'applying operation comprising overlaying the patch over a cutout of the blank, including an interposed active adhesive between the patch and the blank, the character and the amount of the adhesive being such as to retain it within the confines of the periphery of the patch at all forming flaps outlining the envelope body and face of the envelope, a cutout within the said envelope body, and a patch, said patch overlying the cutout in said envelope body by an overlapping portion lying wholly on the interior surface of the envelope blank and extending beyond the periphery of the cutout portion of the blank, but within the outline of the face of the envelope, the

patch being adhesively united to the envelope body at a peripheral edge thereof by adhesive confined within thep'eripheral edge of the patch, and

the peripheral edges of the cutout being united b tothe patch.

21. A window envelope comprising a separately formed envelope, having defined envelope forming flaps outlined in the body of the envelope and the face of the envelope, a cutout within the said 10 envelope body, and a patch, said patch overly-,

ing the cutout in said envelope body by an overlapping portion lying wholly on the interior surface of the envelope blank and extending beyond the periphery of the cutout portion oi? the blank 16 but within the outlines ofthe face or the envelope.

the peripheral edges of the cutout being adhesively united to the patch by adhesive confined between the periphery of the cutout and the periphery of the patch.

22. A window envelope comprising a separately formed envelope blank, having defined envelope forming flaps. outlining the envelope body and race of the envelope, a cutout within the said envelope body, and a patch, said patch overlying the cutout in said envelope body by an overlapping portion lying wholly on the interior surface and exposed inwardly of the envelope blank and extending beyond the periphery of the cutout portion or the blank, but lying, wholly within the 30 outline of the race or the envelope, said patch being adhesively united to the envelope body at the peripheral edge of the patch to'avoid'edges interieringin filling the envelope, by adhesive confined within the peripheral edge of the patch.

23. A window envelope comprising a separatel 5 formed envelope blank, having. defined envelope forming flaps outlining the envelope body, a clitout within said envelope body, and a patch, said patch overlying the cutout in said envelope body by an overlapping portion. lying wholly on the i0 interior surface of the envelope blank and extending beyond the periphery of the cutout portion of the blank, the patch being adhesively united to the envelope body by a illm of adhesive limited to and uniting the peripheral edge of the 15 patch to avoid interfering in filling the envelope. 24. A window envelope comprising a separately formed envelope blank and an adhesive treated,

translucent sheet overlying the out out portion of said envelope) said sheet having an adhesive 20 coating over its entire surface and being united at iits peripheral edgesto the portion of the blank su rounding the window.

25. The method of making window envelopes which comprises .supplyinga web of patch mate- 25 rial adapted to be rendered tacky by heat, heating apatch area of the web, severing it. from'the web, and applying the severed patch while not to an envelope blank.

,- non-r. L. qanr. i 

